WasteWater Operator class C exam
review questions and answers with solutions
2025/2026
When Chlorine is combined with water what type of pipe should be
used?
A. Ductile iron
B. Asbestos concrete
C. PVC
D. Carbon Steel - ANSWER C. PVC
A good settling sludge would consist of what type of protozoa?
A. Rotifers and nematodes
B. Amoebas and Flagellates
C. Stalked ciliates and mastagoria
D. Free swimmers and stalk ciliates - ANSWER D. Free swimmers and
stalk ciliates
What is Phenolphylein used for in titration
,A. Oxidizer
B. Indicator
C. Acid reducer to lower pH
D. Applicator - ANSWER B. Indicator
Your plant has an influent of 220 BOD and 163 TSS, and an effluent of 10
BOD, and 6 TSS. What is the BOD removal efficiency in your plant?
A. 92%
B. 94%
C. 95%
D. 96% - ANSWER C. 95%
You suspect your anaerobic digester is going sour. What is the best way
to verify its condition?
A. pH
B. Foam type
C. VA/ALK ratio
D. DO - ANSWER C. VA/ALK ratio
Before operating any piece of equipment what should be done?
,A. Lock out Tag out (remember, safety first!)
B. Read O & M manual
C. Read manufacturers manual
D. Notify supervisor - ANSWER C. Read manufacturers manual
Detritus is noticed in your grit channel. What is the problem?
A. Velocity too fast with short D/T
B. Velocity too low with long D/T
C. Short circuiting
D. Density currents - ANSWER B. Velocity too low with long D/T
What is considered normal operation of an aerobic digester?
A. Fill react
B. Skim off foam when needed
C. Settle and Decant as needed
D. Feed only during low flow or constant when the sun is out - ANSWER
C. Settle and Decant as needed
A plant with a flow of 1 MGD should be monitored
A. Continuously
, B. Intermittently
C. Daily
D. Every four hours depending on surface load - ANSWER A. Continuously
What do total solids consist of?
A. Dissolved and settleable
B. Floatable and settlable
C. Suspended and dissolved
D. Settlable and nonsettleable - ANSWER C. Suspended and dissolved
What would cause excessive wear on bearing?
A. Misalignment
B. Reduced Oil due to low viscosity
C. Blow seal
D. Over tubercation - ANSWER A. Misalignment
Amperometric titration is used to measure
A. Dissolved solids
B. Chlorine residual
C. Colloids
review questions and answers with solutions
2025/2026
When Chlorine is combined with water what type of pipe should be
used?
A. Ductile iron
B. Asbestos concrete
C. PVC
D. Carbon Steel - ANSWER C. PVC
A good settling sludge would consist of what type of protozoa?
A. Rotifers and nematodes
B. Amoebas and Flagellates
C. Stalked ciliates and mastagoria
D. Free swimmers and stalk ciliates - ANSWER D. Free swimmers and
stalk ciliates
What is Phenolphylein used for in titration
,A. Oxidizer
B. Indicator
C. Acid reducer to lower pH
D. Applicator - ANSWER B. Indicator
Your plant has an influent of 220 BOD and 163 TSS, and an effluent of 10
BOD, and 6 TSS. What is the BOD removal efficiency in your plant?
A. 92%
B. 94%
C. 95%
D. 96% - ANSWER C. 95%
You suspect your anaerobic digester is going sour. What is the best way
to verify its condition?
A. pH
B. Foam type
C. VA/ALK ratio
D. DO - ANSWER C. VA/ALK ratio
Before operating any piece of equipment what should be done?
,A. Lock out Tag out (remember, safety first!)
B. Read O & M manual
C. Read manufacturers manual
D. Notify supervisor - ANSWER C. Read manufacturers manual
Detritus is noticed in your grit channel. What is the problem?
A. Velocity too fast with short D/T
B. Velocity too low with long D/T
C. Short circuiting
D. Density currents - ANSWER B. Velocity too low with long D/T
What is considered normal operation of an aerobic digester?
A. Fill react
B. Skim off foam when needed
C. Settle and Decant as needed
D. Feed only during low flow or constant when the sun is out - ANSWER
C. Settle and Decant as needed
A plant with a flow of 1 MGD should be monitored
A. Continuously
, B. Intermittently
C. Daily
D. Every four hours depending on surface load - ANSWER A. Continuously
What do total solids consist of?
A. Dissolved and settleable
B. Floatable and settlable
C. Suspended and dissolved
D. Settlable and nonsettleable - ANSWER C. Suspended and dissolved
What would cause excessive wear on bearing?
A. Misalignment
B. Reduced Oil due to low viscosity
C. Blow seal
D. Over tubercation - ANSWER A. Misalignment
Amperometric titration is used to measure
A. Dissolved solids
B. Chlorine residual
C. Colloids
